(Bloomberg) -- A prominent donor to Joe Biden’s 2020 campaign has thrown his support to the president’s longshot primary challenger Representative Dean Phillips, according to a person familiar with the matter.

Mike Novogratz, the chief executive officer of Galaxy Investment Partners, a cryptocurrency-focused firm, plans to co-host a campaign fundraiser for Phillips in New York at the home of David Barry, the president and CEO of Urby, a real estate company, added the person, who spoke on condition of anonymity. 

Novogratz told CNBC, which reported his shift to Phillips earlier Tuesday, that he thought both Biden and former President  Donald Trump, the frontrunner for the Republican nomination, were too old to run.

A September Washington Post-ABC News poll found that 74% of adults say the president, who turned 81 in November, would be too old to serve another term, while just 50% say the same of Trump, who is 77. 

Novogratz gave $200,000 to support Biden’s campaign and the Democratic National Committee in 2020, and more than $1 million to Defeat By Tweet, a super political action committee that opposed Trump.

Phillips, a Minnesota congressman first elected in 2018, trails Biden by 69 percentage points according to a November Morning Consult poll.

Read More: Biden Launches Ad Blitz to Counter Voter Worries on Age, Economy

Biden, already the oldest American president in history, has repeatedly insisted he is fit and ready to serve an additional four years as polls show a significant number of voters, including many in his own party, worried about his age.

A November Bloomberg News/Morning Consult poll of almost 5,000 voters across seven swing states found voters more likely to associate Biden with old age than anything else, including his economic agenda. Recent incidents have likely amplified those concerns, including Biden stumbling on stage during a US Air Force Academy graduation ceremony.

The poll found two-thirds of voters believe the running mates for Biden and Trump are more important this year than they have been in past elections given the candidates’ ages. Biden is running for reelection with Vice President Kamala Harris while Trump has not announced a running mate.

Biden’s campaign has hit the airwaves to counter voter perceptions about his health and fitness and to sell his economic agenda with polls showing the public disapproves of his handling of the economy and his approval rating underwater.

--With assistance from Bill Allison.

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